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Learning Target

MS-LSS4-1. Analyze and interpret data for patterns in the fossil record that document the existence, diversity, extinction, and change of life forms throughout the history of life on Earth under the assumption that natural laws operate today as in the past.

MS-ESS1-4. Construct a scientific explanation based on evidence from rock strata for how the geologic time scale is used to organize Earth's 4.6-billion-year-old history

Background

The Earth is a little over 4.5 billion years old, its oldest materials being 4.3 billion-year-old zircon crystals. Its earliest times were geologically violent, and it suffered constant bombardment from meteorites. When this ended, the Earth cooled and its surface solidified to a crust - the first solid rocks. There were no continents as of yet, just a global ocean peppered with small islands. Erosion, sedimentation and volcanic activity - possibly assisted by more meteor impacts - eventually created small proto-continents which grew until they reached roughly their current size 2.5 billion years ago. The continents have since repeatedly collided and been torn apart, so maps of Earth in the distant past are quite different to today's.

The history of life on Earth began about 3.8 billion years ago, initially with single-celled prokaryotic cells, such as bacteria. Multicellular life evolved over a billion years later and it's only in the last 570 million years that the kind of life forms we are familiar with began to evolve, starting with arthropods, followed by fish 530 million years ago (Ma), land plants 475Ma and forests 385Ma. Mammals didn't evolve until 200Ma and our own species, Homo sapiens, only 200,000 years ago. So humans have been around for a mere 0.004% of the Earth's history.

Guiding Questions

Is life independent or dependent of the Earth’s systems?

Ordovician–Silurian Extinction

Around 439 million years ago, 86% of life on Earth was wiped out. Scientists believe two major events resulted in this extinction: glaciation and falling sea levels. Some theories suggest that the Earth was covered in such a vast quantity of plants that they removed too much carbon dioxide from the air which drastically reduced the temperature. Falling sea levels were possibly a result of the Appalachian mountain range forming. The majority of the animal life lived in the ocean. Trilobites, brachiopods, and graptolites died off in large numbers but interestingly, this did not lead to any major species changes during the next era.

Late Devonian Extinction

Estimates propose that around 75% of species were lost around 364 million years ago. Information is unclear as to whether the late Devonian extinction was one single major event or spread over hundreds of thousands of years. Trilobites, which survived the Ordovician-Silurian extinction due to their hard exoskeletons, were nearly exterminated during this extinction. Giant land plants are thought to be responsible as their deep roots released nutrients into the oceans. The nutrient rich waters resulted in mass amounts of algal blooms which depleted the seas of oxygen and therefore, animal life. Volcanic ash is thought to be responsible for cooling earth’s temperatures which killed off the spiders and scorpion-type creatures that had made it on land by this time. A distant amphibian cousin, elpistostegalians, had also ventured onto land but became extinct. Vertebrae did not appear on land again until 10 million years later, the ichthyostegalians from which we all evolved. If the late Devonian extinction had not occurred, humans might not exist today.

Permian–Triassic extinction

This mass extinction, which occurred 251 million years ago, is considered the worst in all history because around 96% of species were lost. Ancient coral species were completely lost. “The Great Dying” was caused by an enormous volcanic eruption that filled the air with carbon dioxide which fed different kinds of bacteria that began emitting large amounts of methane. The Earth warmed, and the oceans became acidic. Life today descended from the 4% of surviving species. After this event, marine life developed a complexity not seen before and snails, urchins, and crabs emerged as new species.

Triassic–Jurassic extinction

The Triassic-Jurassic extinction happened between 199 million and 214 million years ago and as in other mass extinctions, it is believed there were several phases of species loss. The blame has been placed on an asteroid impact, climate change, and flood basalt eruptions. During the beginning of this era, mammals outnumbered dinosaurs. By the end, dinosaurs’ ancestors (archosaurs) reigned the earth’s surface. This extinction laid the path that allowed for the evolution of dinosaurs which later existed for around 135 million years.

Cretaceous–Paleogene extinction

Perhaps the most well-known of the Big 5, the end of the Cretaceous-Paleogene brought on the extinction of dinosaurs. A combination of volcanic activity, asteroid impact, and climate change effectively ended 76% of life on earth 65 million years ago. This extinction period allowed for the evolution of mammals on land and sharks in the sea.

Task 2

Create a 1-2 page paper that outlines the ideas of your exploration into the the development of life on earth and how earth systems affect life on earth in many different ways.

Make sure to use a proper format for your paper. Use the guide below.

7 Components of a Scientific Argument Essay

1. Background
   1. Background information on the topic
2. Claim/Hypothesis/Answer to the guiding question
   1. Your answer to the guiding question that states your argument based on the data/evidence that has been gathered during the investigation
3. Reasoning
   1. Why you chose this as your argument
4. Evidence and Data
   1. The evidence and data that supports your claim
5. Analysis of evidence and data
   1. Discussion of how your evidence supports your claims
6. Conclusions
   1. Restate your claim and relate it back to background, reasoning and evidence
7. Citations
   1. Cite all external sources used in your paper in APA format

Each section should be approximately 3-5 sentences in length.